In general, a centralized storage facility, such a Storage Area Network (SAN), may have several servers attached. Each server may have several storage volumes or file systems. Each volume requires space for its data to grow. An advantage of the SAN is that free storage can be centralized and allocated when needed, thereby reducing the need for unused storage at the installation level. Additional storage can be ordered and installed in one place, then allocated to storage volumes as needed. Underlying mechanics exist for performing storage system allocations and reconfigurations, and in some cases, they may be performed during normal operations. The problem in the art is how much excess storage to keep on hand, and when and where to allocate storage so as to reduce the total need for storage while maintaining a low risk of outage due to lack of storage.